I would say use this, https://github.com/hzrd149/window.nostrdb.js
Its built to auto connect to a local relay at ws://localhost:4869 or fallback to indexeddb. I've been meaning to add support for WASM via @npub1v0lxx...'s worker relay but I haven't figured out how to package it yet

And as @npub1elta7... mentioned I built a small extension that automatically injects the window.nostrdb api 😁

If you don't want to use my magic library then https://github.com/hzrd149/nostr-idb or the @npub1v0lxx...'s worker relay is great

https://hzrd149.github.io/applesauce/examples/#database/worker-relay